Abstract
The overuse of antibiotics in poultry farming has led to the emergence of multidrug-resistant pathogens, posing severe threats to animal health and public safety. Salmonella Pullorum (S. Pullorum), a host-specific pathogen targeting poultry, causes high mortality in chicks and disrupts intestinal health. This study evaluated the protective effects of Bifidobacterium bifidum postbiotics (BbP) against S. Pullorum infection, focusing on their mechanisms in regulating pyroptosis, restoring intestinal barrier function, and modulating gut microbiota. Both in vivo (chickens challenged with S. Pullorum) and in vitro (chicken small intestinal epithelial cells, CSIEC) models were used to assess the effects of BbP and its components (bacterial lysates or metabolites). Results showed that BbP significantly improved growth performance in infected chickens, reducing mortality from 66.66 % to 8.33 %. BbP effectively suppressed the expression of pyroptosis-related proteins, including apoptosis-associated speck-like protein containing a CARD (ASC), Caspase-1 (cysteine-aspartic acid protease-1), and Gasdermin D N-terminal (GSDMD-N), and reduced inflammatory cytokines, including interleukin-1β (IL-1β) and interleukin-8 (IL-8), while increasing anti-inflammatory cytokines, such as interleukin-10 (IL-10) and interleukin-4 (IL-4), thereby mitigating inflammation. Furthermore, BbP restored intestinal barrier function by upregulating the expression of tight junction proteins, including zonula occludens-1 (ZO-1), Occludin, and Claudin-1. The cecal microbiota diversity was also improved by BbP, with a decrease in the abundance of harmful bacteria (e.g., Escherichia-Shigella) and an enrichment of beneficial bacteria (e.g., Lactobacillus and Ruminococcus). These findings demonstrate that BbP provides significant protection against S. Pullorum infection by modulating pyroptosis, protecting the intestinal barrier, and restoring microbial balance. As an effective antibiotic alternative, BbP shows promise for the prevention and control of S. Pullorum infections in poultry farming.